JLuckey(at)pacbell.net
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 Posted: Fri Jan 27, 2012 4:56 pm Post subject: Fuses instead of breakers - too complicated |
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James,
The short answer is: yes, you are getting too complicated.
When you try to do something like that, you must view the situation from every conceivable angle to determine if there is some scenario, however weird or un-likely, that those automatic actions can actually get you into trouble.
Airliners have many systems that interact so that when you do A, B & C happen automatically – however – Airline pilots receive a LOT of systems training and recurrent training.
Having issued that caveat, I have to say (just like I tell my clients - I’m and IT consultant) “we can do (absolutely) anything you want, it just takes time and money”.
-Jeff Luckey
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of James Robinson
Sent: Friday, January 27, 2012 15:34
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: Re: Fuses instead of breakers
Hi Bob
I built a cold air induction for my glasair and will have an alternate filtered air when on the ground. I take off with 10 deg of flaps. Could there be a way to sequence this alternate air door with the flaps? When the flaps come up the the door opens to allow ram air and when the flaps come down it closes the ram air. Am I getting to complicated?
Jim
James Robinson Glasair lll N79R Spanish Fork UT U77
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Friday, January 27, 2012 1:40 PM
Subject: Re: AeroElectric-List: Re: Fuses instead of breakers
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
There is a manual hand pump, so no emergency is created.
Then a robust fuse solution goes toward a cleaner
panel and possibly a cleaner plan B. When THIS
happens, do THAT . . . every time.
>"I have had to do one inflight reset on the Plasma III on one system
>once. The reset was successful and power was restored to the unit. I
>removed the unit and sent it back to Klaus for inspection.
> . . .<snip>
>The point, when the unit faulted it tripped the CB and was then reset
>and provided service throughout the remainder of that flight."
Hmmm. If it immediately resumed functioning after resetting the
breaker, perhaps the ignition never failed, but the heat (and probably
higher currents operating at high temperatures) caused the breaker
to nuisance trip.
The keyword here is "nuisance". I've had to cut the
TC guys some slack for being somewhat submissive to
nuisance trips . . . to strive for the elegant solution
can sometimes be very time consuming and expensive.
One is well advised to trade off cost/benefit ratios.
In the OBAM aircraft world, we're not only able, we are
encouraged to refine any system's configuration in way
that increases the displacement between it's experimental
roots and an enduring recipe for success.
But when one gets a 'nuisance trip' with current protection
that is nearly 2.5 times the published draw numbers . . .
there are reasons to seek answers to some serious questions.
There is a clash of postulates which beg resolution.
They just get extra attention since pilots are more concerned with their
ignition failing than say their nav lights going out 
ABSOLUTELY! Which is why I've recommended that electrically
dependent engine accessories drive from always hot battery
bus with totally independent power paths. If two ignition
systems require power and two batteries are available, then
split the systems between the batteries.
But when a 2A device trips a 5A breaker . . . well . . .
A pullable breaker would stop current flow caused by a stuck relay,
and the manual pump could be used to operate the gear, so there is
no significant flight risk.
Great.
Those relays do look undersized to me.
Better relays might reduce long term maintenance however. Or perhaps
just carry a spare along might be the most practical approach. I think
the latter ?
I thought we were talking about a much larger
hydraulic system. The amount of snort needed to
operate the gear in floats is much smaller than
that used on a GlasAir or Lancair. I think these
relays will be fine and since you have a backup
hand pump, your risks
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